Controller for alternating current motors



Patented Jan. 18, 1949 UNITED STATES PATE NT OFFICE CONTROLLER FOR AL Richard B. Hunter TERNATING CURRENT TORS and Eric Pell, Shorewood, Wis.,

assignors to Cutler-Hammer, Inc., Milwaukee,

is., a corporation of Delawar- Application December 14, 1945, Serial No.

13 Claims. (Cl. 318363) and is particularly advantageous in control of such motors where employed for hoisting and lowering widely varying loads.

For lowering it has been found very advantageous to effect unbalance heavy load.

Another object is size and through the medium of over-voltage which the motor can efficiently stand.

Another object is to Other objects and advantages of the invention will hereinafter appear.

The accompanying drawing illustrates the appended claims. In the drawings, Figure 1 is a diagrammatic view showing in part a known system of control modified to aiford a. preferred form of the control constituting the subject matter of this application;

Fig. 2 shows certain characteristic curves, and

Fig. 3 shows of control.

diagrammatically a, modified form Referring to Fig. 1, the same shows a polyphase motor M having in the circuit of the secondary S thereof resistors R desired in hoisting and of the motor by engagement of interconnected drum segments 26 drum contacts 28 and 29, respectively. Moreover the drum in moving from off Jan. 18, 1949. R. B. HUNTER El AL CONTROLLER FOR ALTERNATING CURRENT MOTORS LOVER Filed Dec:; 14, 1945 (35 I I l 9 6 motor current and thus should be of the electroof the autotransformer to take into account the magnetic type which, of course, could be conadditional voltage of transformer 12. On the trolled in other ways than that illustrated, as other hand, on the first lowering point with conthrough the medium of a hand or foot operated taets 60 to 63 engaged, operation of manual switch switch with or without interlock between such 68 disconnects section II- of the primary oi ness of the former to the first lowering point. that such displacement is in a counterclockwise those skilled in the art. Also it will be apparent representing the voltage of difierent phase now to those. skilled in the art that the control of supplied by the transformer 12, By proper design 3 may have added thereto eatu es of th of transformer Ill and proper connection therecontrol of Fig. 1 which have been omitted for of the voltage and torque conditions may be made simplicity of illustration. to correspond with those obtainable by the con- Referring to Fig. 3, it like Fig. 1 shows a motor trol of Fig. 1. primary P with terminals T T, T to be Suppl ed As will be apparent, the switch 68 is not required from lines L L L through an electroresponto handle the full motor current but only that electrical interconnections of switch 68 and the either circuit immediate closure of the other,

simplicity of illustration, whereas certain addi- Letters Patent 1. rent motor subjected to overhauling loads, a

5 causing said motor at zero speed to produce a former 12 which has a secondary winding 13 connected between motor terminal T and tap 30 of the autotransformer T. The transformer winding ll comprises a section "ll to be connected across lines L and L b drum contacts 64 to 61, or alternatively by cont cts 10 of switch 0 effecting vtfltage unbalapce of h primary 68. Also the primary winding of transformer and on given Speed point causmg S.a1d F at 72 comprises a section II to be connected across zero P to torque m a ,ilrectlon lines 2 and L3 by drum contacts so to 63 and opposite to that m which the overhauling load tends to move, and means associated with the rf l ufe ri g' go i i t i gv t l i the hand or foot 65 o mer means to provide motor connections inoperated switch 5 in normal position as shown, elusive of said autotransformer which cause a its contacts 10 connect Sectlon Ha of the pnmary substantial increase in the afolesaid motor torque, f tran former 12 across lines 1 and 3 as hereand to disconnect said motor from circuit auto- ;ransformer primary and that of its secondary predetermined Value- :vill be of like phase to that of the voltage impress- 3. In com ina i n, a ph s al n n ad on the motor terminals T and T by the autorent motor to be subjected to overhauling loads ranformer T, and the same results as those obof difierent values, a power supply circuit thereained by the control of Fig. 1 on lowering point for, means including an autotransformer to conare obtainable by proper positioning of tap 30 nect said motor to said supply circuit for opposing circuit automatically overhauling loads, and providing selectively a plurality of speed points, said autotransformer effecting voltage unbalance of the motor primary and on a given speed point causing said motor at zero speed to produce a small torque in a direction opposite to that in which the overhauling load tends to move, and means associated with the former means to provide motor connections inclusive of said autotransformer which cause a substantial increase in the aforesaid motor torque, and to disconnect said motor from circuit automatically upon reduction of the motor speed to a predetermined value, the second recited means being efiective Only when the first recited means has a given setting, and said first recited means affording selection of any aforementioned speed point prior to operation of said second recited means to afford increased motor torque.

4-. In combination, a polyphase alternating cur= rent motor to be subjected to overhauling loads, a polyphase supply circuit, an autotransi'ormer, and means to connect said motor to said supply circuit with said autotransformer interposed for voltage unbalancing of the primary of said motor, said autotransformer being in part connected across lines of said supply circuit and having an extended portion, said means providing for se lective connections between certain terminals of said motor and the extended portion of said transformer for causing said motor at zero speed to produce either a small torque or a materially increased torque in a direction opposite to that in which the overhauling load tends to move.

5. In combination, a polyphase alternating current motor to be subjected to overhauling loads of different values, a polyphase supply circuit, means to connect said motor to said supply circuit with said transformer interposed for voltage unbalancing of the primary of said motor, said transformer being in part connected across lines of said supply circuit and having an extended portion, said means afiording selectively connections between certain terminals of said motor and the extended portion of said autotransformer to cause said motor at zero speed to produce either a small torque or a materially increased torque in a direction opposite to that in which the overhauling load tends to move, an electromagnetically controlled friction brake for said motor, and means to disconnect said motor from and to effect setting of said brake when the speed of said motor is reduced to a given value While operating to produce said increased torque.

6. In combination, a polyphase'alternating current motor to be subjected to overhauling loads,

a polyphase supply circuit, an autotransformer, means to connect said motor to said supply circ'uit with said autotransformer interposed for voltage unbalancing of the primary of said motor, said means comprising a master switch movable from an oil position to other positions progressively to establish motor connections inclusive of said autotransiormer which aiTord selectively a relatively high or a relatively low zero speed torque of the motor in a direction opposite to that in which the overhauling load tends to move, said means tending first to establish connections for producing the relatively high torque, and means preventing completion of the latter connections except upon movement of the master switch toward off position.

7. In combination, a polyphase alternating current motor to be subjected to overhauling loads, a polyphase supply circuit, an autotransiormer,

means to connect said motor to said supply circuit with said autotransformer interposed for voltage unbalancing of the primary of said motor, said means comprising a master switch movable from an off position to other positions progressively to establish motor connections inclusive of said autotransformer which afford a relatively high or a relatively low zero speed torque of the motor in a direction opposite to that in which the overhauling load tends to move, and means preventing completion of connections for producing the relatively high torque of the motor except upon movement of the master switch toward oil position, and effecting disconnection of said motor from circuit automatically when its speed is reduced to a given value while operating to produce said relatively high torque.

8. In combination, a polyphase alternating current motor to be subjected to overhauling loads, a polyphase supply circuit therefor, an autotransformer, means to connect said motor to said supply circuit with said autotransformer interposed for voltage unbalancing of the primary of said motor, an additional transformer having a sec ondary winding interposed between said autotransformer and a terminal of said motor, and means selectively to subject the primary of said additional transformer to the voltage of the lines of said circuit supplying said autotransformer thereby to cause said motor to produce at zero speed a relatively small torque or to the voltage of other lines of said circuit thereby to cause said motor to produce at zero speed a substantially higher torque, the torque in each instance being in a direction opposite to that in which the overhauling load tends to move.

9. In combination, a polyphase alternating current motor to be subjected to overhauling loads, a polyphase supply circuit therefor, an autotransformer, means to connect said motor to said supply circuit with said autotransformer interposed for voltage unbalancing of the primary of said motor, an additional transformer having a secondary winding interposed between said autotransformer and a terminal of said motor, and means selectively to subject the primary of said additional transformer to the voltage of the lines of said circuit supplying said autotransformer thereby to cause said motor to produce at zero speed a relatively small torque or to the voltage of other lines of said circuit thereby to cause said motor to produce at zero speed a substantially higher torque, the torque in each instance being in a direction opposite to that in which the overhauling load tends to move, and said means comprising a manually operable switch to commutate the circuit connections of said additional trans,- former and thus {to eiiect either the low or the high'torque excitation of said motor. f,

10. In combination, a polyphase alternating current motor subjected to overhauling loads, a power circuit, means to connect said'motor to said circuit and to afford voltage unbalance of the primary of said motor for motor speed torque characteristics-insuring against reversal of movement of the overhauling load, and means under the control of the former means to coact therewith to aiiord for spotting or checking of the load change in the motor speed torque characteristics thereby to provide at zero motor speed a substantial motor torque in a direction opposite to that in which the load tends to move, the second mentioned means including'means insuring against such action thereof until directed by the first mentioned means as a special step of control suring against reversal subsequent to action of to obtain motor speed the first mentioned means torque characteristics inof movement of the overhauling load.

switch from said on tion.

13. In combination, a polyphase alternating current motor subjected to overhauling loads, a

position toward said ofi posiconnection of said motor from circuit upon reduction of the motor speed to a given value.

RICHARD B. HUNTER. ERIC PELL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 614,394 Kahlenberg Nov. 15, 1898 1,072,422 Burke Sept. 9, 1913 1,446,642 Deutseh Feb. 27, 1923 1,725,849 Cope Aug. 27, 1927 2,228,078 Guiliksen Jan, 7, 1941 2,386,580 Wickerham Oct. 9, 1945 2.386,581 Wickerham Oct. 9, 1945 I 

